Positive-working radiation-sensitive mixture and copying material produced therefrom comprising an α-carbonyl-α-sulfonyl diazomethane, a water-insoluble binder and an acid cleavable compound

ABSTRACT

A positive-working radiation-sensitive mixture is disclosed which contains as essential constituents: 
     a) an α-carbonyl-α-sulfonyl-diazomethane, which forms a strong acid on irradiation, of the general formula I ##STR1##  in which R 1  and R 2 , independently of one another, denote an alkyl-, cycloalkyl-, aryl- or heteroaryl radical 
     b) a compound having at least one C--O--C or C--O--Si bond which can be cleaved by acid, and 
     c) a water-insoluble binder which is soluble or at least swellable in aqueous-alkaline solutions. 
     The radiation-sensitive mixture according to the invention is notable for a high sensitivity over a wide spectral range. It also exhibits a high thermal stability and does not form any corrosive photoylsis products on exposure to light.

This application is a continuation, of application Ser. No. 07/578,778,filed Sept. 7, 1990, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a positive-working radiation-sensitivemixture which contains as essential constituents:

a) a compound which forms a strong acid on irradiation,

b) a compound having at least one C--O--C or C--O--Si bond which can becleaved by acid, and

c) a water-insoluble binder which is soluble or at least swellable inaqueous-alkaline solutions.

The invention also relates to a radiation-sensitive copying materialproduced from this mixture which is suitable for producing photoresists,electronic components, printing plates or for chemical milling.

In UV-lithography, the limit of resolution is governed by the wavelengthof the radiation used. The continuous miniaturization of structuraldimensions, for example, in chip production, therefore requires modifiedlithographic techniques in the submicron region. Owing to their shortwavelength, high-energy UV light or electron beams and X-ray beams, forexample, are used. This modification of the lithographic techniqueschanges the requirements imposed on the radiation-sensitive mixture. Asummary of these requirements is given, for example, in the treatise byC.G. Willson entitled "Organic Resist Materials-Theory and Chemistry"(Introduction to Microlithography, Theory, Materials, and Processing,edited by L. F. Thompson, C. G. Willson, M. J. Bowden, ACS Symp. Ser.,219: 87 (1983), American Chemical Society, Washington). There istherefore an intensified requirement for radiation-sensitive mixtureswhich are preferably sensitive in a wide spectral range and canaccordingly be used in conventional UV lithography or, without a loss insensitivity, in advanced technologies such as, for example, mid-UV ordeep-UV, electron or X-ray lithography.

Mixtures containing acid donors and acid-cleavable compounds aredescribed, for example, in DE 23 06 248 (= U.S. Pat. No. 3,779,778), DE26 10 842 (= U.S. Pat. No. 4,101,323), DE 27 18 254 (= U.S. Pat. No.4,247,611), DE 27 18 259 (= U.S. Pat. No. 4,189,323), DE 29 28 636 (=U.S. Pat. No. 4,311,782), DE 31 51 078 (= U.S. Pat. No. 4,506,006), DE35 44 165 (= U.S. Pat. No. 4,786,577), DE 36 01 264 (= U.S. Pat. No.4,840,867), DE 37 30 783, 37 30 785 and 37 30 787, EP 0 006 626 (= U.S.Pat. No. 4,250,247), EP 0 006 627 (= U.S. Pat. No. 4,248,957), EP 0 042562 (= U.S. Pat. No. 4,506,003), EP 0 202 196 and 0 302 359, and alsoU.S. Pat. No. 4,491,628 and 4,603,101. Upon irradiation of thesematerials, photolysis of the compound (a) forms an acid which bringsabout a cleavage of the C--O--C or C--O--Si bond of the compound (b) sothat the irradiated regions of the photosensitive layers become solublein an aqueous-alkaline developer.

Compounds (a) are characterized as photolytic acid donors and include,in particular, onium salts such as diazonium-, phosphonium-, sulfonium-and iodonium salts of non-nucleophilic acids, for example, of HSbF₆,HAsF₆, or HPF₆ (J. V. Crivello, Polym. Eng. Sci., 23:953 (1983), halogencompounds (EP 0 232 972, DE 15 72 089 (= GB 1 163 324), DE 18 17 540 (=U.S. Pat. No. 3,615,455), DE 19 49 010 (= U.S. Pat. No. 3,686,084), DE23 17 846 (= GB 1 381 471 and 1 381 472), U.S. Pat. No. 3,912,606), inparticular, trichloromethyl triazine derivatives (DE 12 98 414 (= GB 1234 648), DE 22 43 621 (= GB 1 388 492), DE 23 06 248, DE 27 18 259, DE33 33 450 (= ZA 84/7165) and DE 33 37 024 (= U.S. Pat. Nos. 4,619,998and 4,696,888) and also U.S. Pat. Nos. 3,515,552, 3,536,489 and3,615,630) or trichloromethyl oxadiazole derivatives (DE 28 51 472 (=U.S. Pat. Nos. 4,212,970 and 4,232,106), DE 29 49 396 (32 U.S. Pat. No.4,279,982), DE 30 21 590 (= U.S. Pat. No. 4,371,607), DE 30 21 599 (=U.S. Pat. No. 4,371,606) and DE 33 33 450),o-quinonediazidesulfochlorides or organometal/organohalogencombinations.

The use of such photolytic acid donors, however, involves certaindisadvantages which drastically restrict their possible uses in variousfields of application. For example, many of the onium salts are toxic.Their solubility in many solvents is inadequate, which results in alimitation of the choice of resist-coating solvents. If the onium saltsare used, some undesirable foreign atoms are introduced which may resultin processing troubles, in particular in microlithography. Furthermore,during the photolysis they form Bronstedt acids with very strongcorrosive action which render the use of radiation-sensitive mixturescontaining them unsatisfactory on sensitive substrates.

The halogen compounds and also the quinonediazide sulfonyl chloridesform hydrohalic acids with strong corrosive action. On certainsubstrates, such compounds have only a limited storage life. Accordingto the teachings of DE 36 21 376 (= U.S. Pat. No. 4,840,867), this wasimproved in the past by introduction of an intermediate layer betweensubstrate and radiation-sensitive layer containing compounds of the type(a), but this resulted in an undesirable increase in defects and areduction in the process reproducibility. In addition, it was generallybelieved that compounds of the type (b) can be cleaved only by the acidtypes described above which have good mobility in the photosensitivelayer.

Recent work by F. M. Houlihan et al., SPIE 920: 67 (1988) has shownthat, in addition to the above-mentioned acid donors, nitrobenzyltosylates, which form sulfonic acids of low mobility on exposure tolight, can be used in certain acid-labile resist formulations. Thesensitivities achieved in such cases and the thermal stabilities of thephotoresists have, however, proven inadequate.

Owing to the disadvantages cited there is therefore a need for furtheracid donors which act photolytically, which do not have thedisadvantages described above as constituents of radiationsensitivemixtures and which consequently have sufficient reactivity and acidstrength to convert compounds of the type (b) into their cleavageproducts even with short exposure times.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide aradiation-sensitive mixture based on acid-forming compounds incombination with compounds which can be cleaved by acid, in whichmixture the compound which forms an acid photolytically is as stable aspossible on all known substrates and generates an acid with noncorrosiveaction as the photolytic product.

In accomplishing these and are other objects according to the inventionthere is provided a positive-working radiation-sensitive mixtureconsisting essentially of a) a compound which forms an acid onirradiation, b) a compound having at least one C--O--C or C--O--Si bondwhich can be cleaved by acid, and c) a water-insoluble binder which issoluble or at least swellable in aqueous-alkaline solutions, whereincompound (q) is an α-carbonyl-α-sulfonyldiazomethane of the generalformula I ##STR2## in which R¹ and R², independently of one another,denote an alkyl-, cycloalkyl-, aryl- or heteroaryl radical. Apositive-working radiation-sensitive copying material consistingessentially of a layer of this radiation-hardenable mixture coated on asupport is also provided in accordance with the present invention.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A radiation-sensitive mixture according to the invention contains asessential constituents:

a) a compound which forms a strong acid on exposure to actinicradiation,

b) a compound having at least one C--O--C or C--O--Si bond which can becleaved by acid, and

c) a water-insoluble binder which is soluble or at least swellableaqueous-alkaline solutions.

The compound (a) which forms a strong acid on irradiation is anα-carbonyl-α-sulfonyl-diazomethane of the general formula I ##STR3## inwhich R¹ and R² denote an optionally substituted alkyl, cycloalkyl, arylor heteroaryl radical, it being not necessary for R¹ and R² to beidentical.

A radiation-sensitive copying material according to the inventioncontains this mixture as a radiation-sensitive layer on a suitablesupport.

The radiation-sensitive mixture according to the invention has a highsensitivity over a wide spectral range. It exhibits a high thermalstability and is capable of reproducing even the finest structures of amaster with structural precision. No corrosive photolysis products areformed by the exposure to light, with the result that the mixture can beused even on sensitive substrate materials.

In the preparation of the radiation-sensitive mixture, it is possible touse compounds of the general formula I in which R¹ and R² denote,independently of one another, an optionally substituted alkyl orcycloalkyl radical, an optionally substituted aryl radical or anoptionally substituted heteroaryl radical.

Examples of suitable substituents R¹ and R² inα-carbonyl-α-sulfonyl-diazomethanes of the general formula I includemethyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, nonyl, decyl orundecyl groups, and also their positional isomers; as well as benzeneand naphthalene and their derivatives in which one or more hydrogenatoms are substituted, for example, by alkyl, alkoxy, alkoxyalkyl, aryl,aryloxy, arylalkoxy, halo, cyano, nitro, carbonyl, carboxyl or similarradicals. Particularly preferred substituents are alkyl, alkoxy,alkoxyalkyl, halogens, in particular chlorine or bromine, and cyano,where the alkyl or alkoxy radicals contain in particular 1 to 3 carbonatoms.

Among the compounds of the general formula I those are preferred inwhich R¹ and R², independently of one another, comprise an alkyl radicalwith 1 to 6 carbon atoms or an optionally substituted aryl radical, andin which at least one of the radicals R¹ and R² represents an optionallysubstituted aryl radical, with mono- or binuclear aryl radicals beingparticularly preferred.

Particular preference is given to compounds of the general formula Iwhere R¹ and R², independently of one another, represent at least oneoptionally substituted aryl radical, especially:

methylsulfonyl-benzoyl-diazomethane

ethylsulfonyl-benzoyl-diazomethane

methylsulfonyl-4-bromobenzoyl-diazomethane

ethylsulfonyl-4-bromobenzoyl-diazomethane

phenylsulfonyl-benzoyl-diazomethane

phenylsulfonyl-m-toluoyl-diazomethane

phenylsulfonyl-p-toluoyl-diazomethane

phenylsulfonyl-3--methoxybenzoyl-diazomethane

phenylsulfonyl-4-methoxybenzoyl-diazomethane

phenylsulfonyl-3-chlorobenzoyl-diazomethane

phenylsulfonyl-4-chlorobenzoyl-diazomethane

phenylsulfonyl-2-bromobenzoyl-diazomethane

phenylsulfonyl-3-bromobenzoyl-diazomethane

phenylsulfonyl-4-bromobenzoyl-diazomethane

phenylsulfonyl-4-cyanobenzoyl-diazomethane

phenylsulfonyl-1-naphthoyl-diazomethane

phenylsulfonyl-2-naphthoyl-diazomethane

p-tolylsulfonyl-benzoyl-diazomethane

p-tolylsulfonyl-m-toluoyl--diazomethane

p-tolylsulfonyl-p-toluoyl-diazomethane

p-tolylsulfonyl-3-methoxybenzoyl-diazomethane

p-tolylsulfonyl--4--methoxybenzoyl-diazomethane

p-tolylsulfonyl-3-chlorobenzoyl-diazomethane

p-tolylsulfonyl-4-chlorobenzoyl-diazomethane

p-tolylsulfonyl-2-bromobenzoyl-diazomethane

p-tolylsulfonyl-3-bromobenzoyl-diazomethane

p-tolylsulfonyl-4-bromobenzoyl-diazomethane

p-tolylsulfonyl-4--cyanobenzoyl-diazomethane

p-tolylsulfonyl-l-naphthoyl-diazomethane

p-tolylsulfonyl-2-naphthoyl-diazomethane

These compounds are particularly suitable because, on the one hand, theyhave a high photolysis reactivity, and, on the other hand, they have anadequate thermal stability.

The preparation of the α-carbonyl-α-sulfonyl-diazomethane derivativesused according to the invention is known per se. Their preparation hasbeen described, for example, by W. Illger, A. Liedgehegener and M.Regitz, Ann., 760: 1 (1972). A survey of their preparation andproperties has been given by M. Regitz and G. Maas in Diazo Compounds,Properties and Synthesis, Academic Press, Orlando, 1986.

In addition, their use as dissolution inhibitors for positive-workingmaterials, in particular for printing plates, has been investigated inthe past by A. Poot et al., J. Photogr. Sci., 19: 88 (1971); theirpractical suitability in photoresist formulations was, however, rulesout because of inadequate photosensitivity.

It was therefore particularly surprising that the compounds of thegeneral formual I used according to the invention form, during theirphotolysis, adequate quantities of sufficiently strong acids which makeit possible to produce the highly sensitive, positive-workingradiation-sensitive mixture according to the invention. Although thereare no precise ideas about the extent and the nature of the acidsformed, it may be assumed that sulfonic and sulfinic acids form as aresult of the photolysis.

Compared with the photolytically produced acids hiterhto used such as,for example, hydrochloric acid, these acids have, as a consequence oftheir high molecular weight, a much lower diffusion tendency or mobilityin the radiation-sensitive mixture according to the invention. It wassurprising that it was possible to achieve an image differentiationsatisfying the highest requirements, and even more surprising that, at acomparable sensitivity, the contrast, and consequently the resolvingpower, of the radiation-sensitive mixture was increased further. It wasalso surprising that the α-carbonyl-α-sulfonyldiazomethanes of thegeneral formula I can be activated by high-energy short-wave radiation.This makes it possible, for example, to produce a highly sensitivephotoresist for high-energy UV2 radiation (248 nm). In particular,however, it was unexpected that an adequate spectral sensitivity isstill present even in the conventional optical lithography region (436nm).

In this connection, actinic radiation is to be understood to mean anyradiation whose energy is equivalent at least to that of short-wavevisible light. In particular, UV radiation in the range from 190 to 450nm, preferably from 200 to 400 nm, particularly preferably from 200 to300 nm, but also electron radiation and X-rays are suitable.

The preparation of the α-carbonyl-α-sulfonyldiazomethanes used accordingto the invention, some of which are novel, is illustrated on the basisof the preferred P-Phenylsulfonyl-4-bromobenzoyl-diazomethane (pbw=partsby weight). In this preparation, 27.8 pbw of 4-bromophenacyl bromide and16.4 pbw of sodium benzene sulfinate are suspended in 250 pbw ethanoland heated under reflux for 5 hours. The warm solution is filtered.After cooling, the resulting precipitate is isolated by suction andrecrystallized from ethanol. Almost colorless crystals are obtained(25.5 pbw), which are analytically purephenylsulfonyl-(4-bromobenzoyl)-methane.

The resulting product (10 pbw) is dissolved together with 4.8 pbw oftosylazide in 90 pbw of acetonitrile and cooled to 0° C. Triethylamine(2.5 pbw) are added dropwise to this mixture in a manner such that thetemperature remains below 10° C. Stirring of the mixture is continuedfor 8 hours at room temperature and the solvent is then removed from themixture. The residue is taken up in methylene chloride and extractedtwice with 100 pbw of 5%-strength aqueous sodium hydroxide solution,washed until neutral and dried. After evaporating the solvent, 7.5 pbwof pale yellowish crystals having a decomposition temperature of 122° C.are obtained, which are analytically purephenylsulfonyl-(4-bromobenzoyl)-diazomethane.

The analysis of this compound yielded the following values:

calc.: C 46.02%, H 2.47%, N 7.67%, S 8.76%, Br 21.91%

found: C 47.1%, H 2.3%, N 7.5%, S 8.4%, Br 22.7%

¹ H-NMR (CDCl₃): 7.4-8.2 ppm (m, 9 H).

λ_(max) (CHCl₃)=242 nm.

The other above-mentioned compounds of the general formula I can beprepared in analogous manner.

One or more photolytic acid donors according to Formula I can becontained in the radiation-sensitive mixture according to the invention.Combinations with other photolytic acid donors are, however, alsopossible, for which purpose, in particular, theα,α-bis-sulfonyl-diazomethanes described in copending U.S. applicationSer. No. 07/578,465 filed Sep. 7, 1980 ; corresponding to GermanApplication P 39 30 086.2 and filed simultaneously herewith aresuitable.

In addition, the acid donors of the general formula I according to theinvention can also be combined with onium salts such as diazonium,phosphonium, sulfonium and iodonium salts of non-nucleophilic acids, forexample, of HSbF₆ HAsF₆, or HPF₆ (J. V. Crivello, Polym. Eng. Sci., 23:953 (1983), halogen compounds (EP 0 232 972, DE 15 72 089, DE 18 17 540,DE 19 49 010, U.S. Pat. No. 3,912,606, DE 23 17 846), in particular,trichloromethyl triazine derivatives (U.S. Pat. Nos. 3,515,552,3,536,489, 3,615,630 and 3,779,778, DE 27 18 259, DE 33 37 024, DE 33 33450, DE 23 06 248, DE 22 43 621, DE 12 98 414) ortrichloromethyloxadiazole derivatives (DE 30 21 590, DE 30 21 599, DE 2851 472, DE 29 49 396, DE 33 33 450, EP 135 348),o-quinone-diazidesulfochlorides or organometal/organohalogencombinations. Such combinations are not, however, preferred, since thedisadvantages mentioned in the background occur in suchradiation-sensitive mixtures.

The content of acid donors of the general formula I in the mixtureaccording to the invention is in general between about 0.5 and 25% byweight, preferably about 1 to 10% by weight, based in each case on thetotal weight of the layer.

As the material which can be cleaved by acid in the radiation-sensitivemixture according to the invention the following compound categories, inparticular, have proven successful:

a) those containing at least one orthocarboxylic acid ester and/orcarboxylic acid amide acetal grouping, the compounds also being capableof having a polymeric nature and the groupings mentioned being capableof occurring as linking elements in the main chain or as lateralsubstituents,

b) oligomeric or polymeric compounds containing repeating acetal and/orketal groupings in the main chain,

c) compounds containing at least one enol ether or N-acyliminocarbonategrouping,

d) cyclic acetals or ketals of β-keto esters or β-keto amides,

e) compounds containing silyl ether groupings,

f) compounds containing silyl enol ether groupings,

g) monoacetals or monoketals whose aldehydes or ketone components have asolubility in the developer of between 0.1 and 100 g/l,

h) ethers based on tertiary alcohols, and

i) carboxylic acid esters and carbonates of

tertiary allylic or benzylic alcohols.

As components of radiation-sensitive

As mixtures, compounds of type (a) which can be cleaved by acids aredescribed in detail in DE 26 10 842 and 29 28 636. Mixtures whichcontain compounds of type (b) are disclosed in DE 23 06 248 and 27 18254. Compounds of type (c) are described in EP 0 006 626 and 0 006 627.Compounds of type (d) are disclosed in EP 0 202 196, and compounds oftype (e) are disclosed in DE 35 44 165 and 36 01 264. Compounds of type(f) are found in DE 37 30 785 and 37 30 783, while compounds of type (g)are dealt with in DE 37 30 787. Compounds of type (h) are described, forexample, in U.S. Pat. No. 4,603,101, and compounds of type (i), forexample, in U.S. Pat. No. 4,491,628 and also in J. M. Frechet et al., J.Imaging Sci., 30: 59-64 (1986).

Mixtures of the materials mentioned which can be cleaved by acids mayalso be used. Preferred, however, is a material of one of theabovementioned types, having a C--O--C bond which can be cleaved byacid. Particularly preferred are materials of types (a), (b), (g) and(i). Among type (b), the polymeric acetals must, in particular, behighlighted; of the materials of the type (g) which can be cleaved byacid, in particular those whose aldehyde or ketone component has aboiling point of higher than 150° C., preferably higher than 200° C.,must be highlighted.

The content of material which can be cleaved by acid in theradiation-sensitive mixture according to the invention should be about 1to 50% by weight, preferably about 5 to 25% by weight, based in eachcase on the total weight of the layer.

The radiation-sensitive mixture according to the invention also containsat least one polymeric water-insoluble binder which is soluble, or atleast swellable, in aqueous-alkaline solutions. The binder isdistinguished, in particular, by the fact that it readily dissolves theconstituents of the radiation-sensitive mixture according to theinvention and has inherent absorption that is as low as possible, i.e.,high transparency, in particular in the wavelength range from 190 to 300nm. This does not include, in particular, those binders based on novolakcondensation resins which have been used, as a rule, in combinations ofnaphthoquinonediazides as photoactive components. Although novolakcondensation resins reveal a drop in solubility in aqueous-alkalinedevelopers in the unexposed regions after exposure to an image, theirinherent absorption is undesirably high in the wavelength range requiredfor the exposure to light.

The novolak condensation resins mentioned may, however, be used in amixture with other resins having high transparency and being suitable asbinders. In this connection, the mixing ratios depend predominantly onthe nature of the binder to be mixed with the novolak resin. Inparticular, a decisive role is played by its degree of inherentabsorption in the wavelength range mentioned, and also by itsmiscibility with the other constituents of the radiation-sensitivemixture. In general, however, the binder of the radiation-sensitivemixture according to the invention may contain up to about 30% byweight, in particular up to about 20% by weight, of a novolakcondensation resin.

Suitable binders are homopolymers or copolymers of p-hydroxystyrene andalso of its alkyl derivatives, for example, of 3-methylhydroxystyrene,and also homopolymers or copolymers of other polyvinylphenols, forexample, of 3-hydroxystyrene or the esters or amides of acrylic acidswith aromatics containing phenolic groups. Polymerizable compounds suchas styrene, methacrylic acid methacrylate, acrylic acid methacrylate orthe like can be used as comonomers in the copolymer.

Mixtures with increased resistance to plasma etching are obtained ifvinyl monomers containing silicon, for example, vinyltrimethylsilane,are used to prepare copolymers of the above type. The transparency ofthese binders is generally higher in the range of interest, with theresult that an improved patterning is possible.

Homopolymers or copolymers of maleinimide can also be used with the samesuccess. These binders also exhibit high transparency in the wavelengthrange described. Styrene, substituted styrenes, vinyl ethers, vinylesters, vinylsilyl compounds or (meth)acrylic acid esters are also usedas comonomers.

Finally, it is also possible to use copolymers of styrene withcomonomers which bring about an increase in solubility inaqueous-alkaline solutions. These include, for example, maleicanhydride, maleic acid half-esters or the like.

The binders mentioned may occur in mixtures if they are miscible and donot impair the optical qualities of the radiation-sensitive mixture.Preferred, however, are binders containing one species of theabove-mentioned types.

The quantity of binder is, in general, about 1 to 90% by weight, inparticular about 5 to 90% by weight, preferably about 50 to 90% byweight, based on the total weight of the radiation-sensitive mixture.

Optionally, dyestuffs, pigments, wetting agents and levelling agents,but also polyglycols, cellulose ethers, for example, ethylcellulose, maybe added to the radiation-sensitive mixtures according to the inventionto improve specific requirements such as flexibility, adherence andluster.

Preferably, the radiation-sensitive mixture according to the inventionis dissolved in solvents, for example, ethylene glycol, glycol ether,glycol monomethyl ether, glycol dimethyl ether, glycol monoethyl etheror propylene glycol monoalkyl ether, in particular propylene glycolmethyl ether, aliphatic esters, for example, ethyl acetate, hydroxyethylacetate, alkoxyethyl acetate, n-butyl acetate, propylene glycolmonoalkyl ether acetate, in particular propylene glycol methyl etheracetate or amyl acetate, ethers, for example, dioxan, ketones forexample, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone andcyclohexanone, dimethylformamide, dimethyl acetamide,hexamethylphosphoric acid triamide, N-methylpyrrolidone, butyrolactone,tetrahydrofuran and mixtures of the same. Particularly preferred areglycol ether, aliphatic esters and also ketones.

Ultimately the choice of solvents depends on the coating method used,the desired layer thickness and the drying conditions. The solvent mustalso be chemically neutral, i.e., it must not react irreversibly withthe other layer components.

The solutions produced with the constituents of the radiation-sensitivemixture generally have a solids content of about 5 to 60% by weight,preferably up to about 50% by weight.

According to the invention, a radiation-sensitive copying material isproduced by coating a substrate with a layer of the radiation-sensitivemixture. Suitable substrates are all those materials of whichcapacitors, semiconductors, multilayer printed circuits or integratedcircuits are composed or from which they are produced. In particular,mention may be made of surfaces composed of thermally oxidized siliconmaterial and/or silicon material coated with aluminum which mayoptionally also be doped, and including all the other substrates commonin semiconductor technology such as, for example, silicon nitride,gallium arsenide and indium phosphide. Furthermore, the substrates knownfrom liquid crystal display production such as, for example, glass andindium tin oxide, metal plates and metal foils, for example, ofaluminum, copper or zinc, bimetal and trimetal foils, and alsoelectrically nonconducting sheets vapor-coated with metals, SiO₂materials optionally coated with aluminum, and paper, are suitable.These substrates may be subjected to a thermal pretreatment,superficially roughened, incipiently etched or treated with reagents toimprove the desired properties, for example, to increase the hydrophilicnature.

In a particular embodiment, the radiation-sensitive mixture may containan adhesion promoter to improve adhesion in the resist or between theresist and the substrate. In the case of silicon or silicon dioxidesubstrates, adhesion promoters of the aminosilane type such as3-aminopropyltriethoxysilane or hexamethyldisilazane are suitable forthis purpose.

Examples of supports which can be used to produce photomechanicalcopying layers such as printing forms for letterpress printing,lithographic printing and screen printing and also of embossed copiesare aluminum plates, optionally anodically oxidized, grained and/orsilicatized, zinc plates and steel plates which have optionally beenchromium-plated, and also plastic sheets or paper.

The copying material according to the invention is exposed to an image.Sources of actinic radiation include metal halide lamps, carbon arclamps, xenon lamps and mercury vapor lamps. An exposure to high-energyradiation such as laser radiation, electron radiation or X-rays may alsotake place. Particularly preferred, however, are lamps which are able toradiate light of a wavelength from 190 to 260 nm, i.e., in particularxenon and/or mercury vapor lamps. In addition, laser light sources, forexample, excimer lasers, in particular KrF or ArF lasers which emit at249 or 193 nm respectively, may also be used. The radiation sources musthave an adequate emission in the wavelength ranges mentioned.

The layer thickness varies as a function of its field of application. Itis between about 0.1 and 100 μm, in particular between about 1 and 10μm.

The invention also relates to a method of producing aradiation-sensitive copying material. The radiation-sensitive mixturecan be applied to the substrate by spraying-on, flow coating, rolling,spin-coating or immersion coating. The solvent is then removed byevaporation, with the result that the radiation-sensitive layer remainsbehind on the surface of the substrate. The removal of the solvent canbe promoted by heating the layer to temperatures of up to about 150° C.The mixture may, however, first be applied in the above mentioned mannerto an intermediate support from which it is transferred under pressureand elevated temperature to the final support material. As intermediatebases, all the materials also identified as base materials can be used.The layer is then irradiated according to an image. An image pattern isrevealed in the radiation-sensitive layer by development, the layerbeing treated with a developer solution which dissolves or removes theirradiated regions of the material.

As developers, solutions of reagents such as, for example, silicates,metasilicates, hydroxides, hydrogen- or dihydrogenphosphates, carbonatesor hydrogencarbonates, of alkali metals and/or alkaline earth metals, inparticular of ammonium ions, but also ammonia and the like are used.Metal-ion-free developers are described in U.S. Pat. No. 4,729,941, EP 0062 733, U.S. Pat. Nos. 4,628,023, 4,141,733, EP 0 097 282 and EP 0 023758. The content of these substances in the developer solution isgenerally about 0.1 to 15% by weight, preferably about 0.5 to 5% byweight, based on the weight of the developer solution. Metal-ion-freedevelopers are used in particular. Optionally, minor quantities of awetting agent may be added to the developers in order to facilitate thedissolution of the exposed areas in the developer.

The developed resist structures are optionally post-hardened. This isdone, in general, by heating the resist structure on a hot plate to atemperature below the flow temperature and then exposing it to the UVlight of a xenon-mercury vapor lamp (range from 200 to 250 nm) over itswhole area. This post-hardening crosslinks the resist structures withthe result that the structures generally have a flow resistance up totemperatures of over 200° C. The post-hardening may also be carried outwithout raising the temperature by irradiation with high-energy UVlight.

The radiation-sensitive mixture is preferably used in lithographicprocesses for producing integrated circuits or discrete electricalcomponents. The copying material produced from the mixture then servesas a mask for the subsequent processing steps. These include, forexample, the etching of the support, the implantation of ions in thesupport or the deposition of metals or other materials on the support.

The examples described below are illustrative of the invention and arenot intended to be limiting. Examples 1 to 8 confirm the suitability ofthe mixture according to the invention for copying materials inmicrolithography using radiation of a very wide range of energy.Comparison Examples 9 and 10 confirm the superiority of the mixtureaccording to the invention over the prior art. Examples 11 and 12document the usability of the mixture in printed circuits andlithographic printing plates.

EXAMPLE 1

A coating solution was prepared from

    ______________________________________                                        7.5   pbw      of a cresol-formaldehyde novolak having                                       a softening range of 105 to 120° C.,                    2.0   pbw      of p-methoxybenzaldehyde                                                      bis(phenoxyethyl)acetal, prepared                                             analogously to Preparation Example 1 of                                       DE 37 30 787, and                                              0.7   pbw      of phenylsulfonyl-4-methoxybenzoyl-                                           diazomethane in                                                42    pbw      of propylene glycol monomethyl ether                                          acetate.                                                       ______________________________________                                    

The solution was filtered through a filter having a pore diameter of 0.2μm and spun onto a wafer treated with an adhesion promoter(hexamethyldisilazane) at 3,200 revolutions per minute. After drying at100° C for 1 minute on a hot plate, a layer thickness of 1.1 μm wasobtained.

The copying material was exposed to an image under a master using the UVradiation of a xenon-mercury vapor lamp at 365 nm having an energy of 80mJ/cm².

The copying material was developed with a 0.3 N alkaline developer ofthe following composition:

5.3 pbw of sodium metasilicate nonahydrate,

3.4 pbw of trisodium phosphate dodecahydrate,

0.3 pbw of sodium dihydrogenphosphate and

91 pbw of completely softened water.

After a development time of 60 seconds, a fault-free image of the maskhaving steep resist edges was obtained, even structures of less than 1μm being resolved in true detail. An examination of the edges of theresist profiles by means of scanning electron microscopy confirmed thatthese were virtually perpendicular to the substrate surface.

EXAMPLE 2

A coating solution was prepared from

    ______________________________________                                        7.5   pbw      of a copolymer of styrene/p-                                                  hydroxystyrene (20/80) having an average                                      molecular weight of 32,000,                                    2.0   pbw      of 3,4-dimethoxybenzaldehyde                                                  bis(phenoxyethyl)acetal prepared                                              analogously to Preparation Example 1 of                                       DE 37 30 787 and                                               0.7   pbw      of phenylsulfonyl-toluoyl-diazomethane                                        in                                                             42    pbw      of propylene glycol monomethyl ether                                          acetate.                                                       ______________________________________                                    

The solution was filtered through a filter having a pore diameter of 0.2μm and spun onto a wafer treated with an adhesion promoter(hexamethyldisilazane) at 3,000 revolutions per minute. After drying at100° C. for 1 minute on a hot plate, a layer thickness of 1.12 μm wasobtained.

The copying material was exposed to an image under a master using the UVradiation of a xenon-mercury vapor lamp at 260 nm having an energy of 92mJ/cm² and then processed with the developer described in Example 1.

After a development time of 60 seconds, a fault-free image of the maskhaving high edge stability was obtained, structures of less than 1 μmalso being resolved in true detail.

EXAMPLE 3

A wafer prepared in accordance with Example 1 was irradiated under amaster using UV light having a wavelength of 405 nm with an energy of100 mJ/cm³. After development, an image of the master in which thestructures were reproduced in true detail was obtained.

EXAMPLE 4

The experiment of Example 3 was repeated, but UV light of a wavelengthof 436 nm was used. In order to obtain an image of the master with steepedges, an exposure energy of 250 mJ/cm² had to be used.

EXAMPLE 5

A coating solution was prepared from

    ______________________________________                                        7.5   pbw      of a 1:1 copolymer of styrene and                                             maleimide having a softening range of                                         165 to 180° C.,                                         2.0   pbw      of benzaldehyde bis(phenoxyethyl)acetal                                       prepared analogously to Preparation                                           Example 1 of DE 37 30 787, and                                 0.7   pbw      of phenylsulfonyl-(4-chlorobenzoyl)-                                          diazomethane in                                                42    pbw      of propylene glycol monomethyl ether                                          acetate.                                                       ______________________________________                                    

The solution was filtered through a filter having a pore diameter of 0.2μm and spun onto a wafer treated with an adhesion promoter(hexamethyldisilazane) at 3,700 revolutions per minute. After drying at100° C. for 1 minute on a hot plate, a layer thickness of 0.98 μm wasobtained.

The copying material was exposed to an image under a master using theLrV radiation of a xenon-mercury vapor lamp at 260 nm having an energyof 120 mJ/cm².

The copying material was developed with a 0.02 N aqueous solution oftetramethyl ammonium hydroxide, the exposed regions being removed toleave no residue within 60 seconds.

Once more a fault-free image of the mask with steep resist edges wasobtained. The removal of unexposed area was less than 20 nm; evenstructures of less than 1 μm were resolved in true detail.

EXAMPLE 6

A coating solution was prepared from

    ______________________________________                                        7.5   pbw      of a 1:1 copolymer of styrene and                                             maleimide having a softening range of                                         165 to 180° C.,                                         2.0   pbw      of 3,4-methylenedioxybenzaldehyde                                             bis(phenoxyethyl)acetal,                                       0.8   pbw      of 2-naphthoyl-phenylsulfonyl-                                                diazomethane in                                                42    pbw      of propylene glycol monomethyl ether                                          acetate.                                                       ______________________________________                                    

The solution was filtered through a filter having a pore diameter of 0.2μm and spun onto a wafer treated with an adhesion promoter(hexamethyldisilazane) at 3,500 revolutions per minute. After drying at100° C. for 1 minute on a hot plate, a layer thickness of 1.00 μm wasobtained.

The copying material was exposed to an image under a master using theLrV radiation of a xenon-mercury vapor lamp at 260 nm having an energyof 102 mJ/cm².

The copying material was developed with a 0.02 N aqueous solution oftetramethyl ammonium hydroxide, the exposed regions being removed toleave no residue within 60 seconds and a true-to-detail image of themaster being obtained. The edge steepness of the image was excellent.

EXAMPLE 7

A coating solution was prepared from

    ______________________________________                                        7.5   pbw      of the copolymer described in Example 2,                       2.0   pbw      of a polyorthoester, prepared by con-                                         densation, of 1 mol of 7,7-                                                   bishydroxymethylnonanol with 1 mol of                                         methyl orthoformate,                                           0.8   pbw      of 4-bromobenzoyl-phenylsulfonyl-                                             diazomethane in                                                42    pbw      of propylene glycol monomethyl ether                                          acetate.                                                       ______________________________________                                    

The solution was filtered through a filter having a pore diameter of 0.2μm and spun onto a wafer treated with an adhesion promoter(hexamethyldisilazane) at 3,500 revolutions per minute. After drying at100° C. for 1 minute on a hot plate, a layer thickness of 1.04 μm wasobtained.

The copying material was exposed to an image under a master using the UVradiation of a xenon-mercury vapor lamp at 260 nm having an energy of112 mJ/cm².

The copying material was developed with a 0.27 N aqueous solution oftetramethylammonium hydroxide, the exposed areas being removed to leaveno residue within 60 seconds and a true-to-detail image of the masterbeing obtained. Lines and gaps down to 0.7 μm were reproduced withfaithfulness to the mask.

EXAMPLE 8

The copying material from Example 7 was irradiated with synchrotronradiation (BESSY, Berlin, 754 MeV) through a gold-on-silicon mask with adose of 180 mJ/cm². The experimental setup can be found in A. Heuberger,Microelectr. Eng., 3: 535 (1985). After development with the developerdescribed in Example 7 and a development time of 70 seconds, afault-free image of the mask was obtained down to structures of lessthan 0.6 μm. The resist edges were virtually vertical to the planarsubstrate surface.

EXAMPLES 9 AND 10 (COMPARISON EXAMPLES)

The resist formulation of Example 7 was modified by replacing theacid-forming compound by an equal quantity of triphenylsulfoniumhexafluorophosphate (Example 9) or 2-nitrobenzyl tosylate (Example 10).

After exposure to radiation of a wavelength of 260 nm and an energy of105 or 140 mJ/cm² and development with a developer of the compositionspecified in Example 1, structures which exhibited no imagedifferentiation suitable for practical work were obtained.

On using the onium salt (Example 9), structures with so-called "resistfoot" were obtained, i.e., resist residues adhered to the substrate inthe exposed regions, while on using the tosyl ester (Example 10) surfacecrosslinkings ("lips") were visible and these spanned the substrateareas which had been bared. In both cases no acceptable patterning wasobtained.

EXAMPLE 11

To prepare an offset printing plate, a mechanically roughened andpre-treated aluminum foil was spin-coated with a coating solution of thecomposition below:

    ______________________________________                                        7.5    pbw      of a cresol-formaldehyde novolak having                                       a softening range of 105 to 120° C.,                   2.3    pbw      of p-methoxybenzaldehyde-                                                     bis(phenoxyethyl)-acetal,                                     0.5    pbw      of phenylsulfonyl-4-bromobenzoyl-                                             diazomethane,                                                 0.05   pbw      of crystal violet base in                                     90     pbw      of propylene glycol monomethyl ether                                          acetate.                                                      ______________________________________                                    

After drying the layer (layer weight approximately 2.5 g/m²), exposurewas carried out under a positive test master for 30 seconds anddevelopment was then carried out with a developer of the followingcomposition:

    ______________________________________                                        0.5     pbw      of sodium hydroxide,                                         0.8     pbw      of sodium metasilicate nonahydrate,                          1.0     pbw      of 2-n-butoxyethanol in                                      97.7    pbw      of completely softened water.                                ______________________________________                                    

After rinsing with water, the plate was made ready for printing bywiping over with 1%-strength phosphoric acid. After clamping in aprinting press, 55,000 perfect prints of the master were obtained.

EXAMPLE 12

The solution of an etch and electroplating positive dry resist wasprepared by making up the following composition:

    ______________________________________                                        12.5   pbw      of the novolak described in Example 11,                       10.0   pbw      of an oligomeric aliphatic polyacetal                                         having a mean molecular weight of                                             approximately 1,400 prepared by                                               condensation of butyraldehyde with                                            diethylene glycol,                                            0.5    pbw      of phenylsulfonyl-4-t-butylbenzoyl-                                           diazomethane,                                                 0.1    pbw      of crystal violet in                                          25     pbw      of butanone.                                                  ______________________________________                                    

A polyethylene terephthalate film of 25 μm thickness, which is standardfor this purpose, was coated with this solution, with the result that adry layer thickness of 18 μm was produced. The surface of the dry resistfilm was clad with a further polyethylene terephthalate film. The dryfilm was laminated onto a brass sheet after peeling off the coveringfilm under pressure and heat. After cooling and peeling off thetemporary support film, the sheet was exposed through a master, in whichprocess a good image contrast became visible. The exposed areas werespray-developed with a developer of the composition specified in Example11. The sheet was then etched with commercial ferrichloride solutionuntil the smooth edges had been etched through. The shaped partsobtained may be processed still further before separation into singles.

What is claimed is:
 1. A positive-working radiation-sensitive mixtureconsisting essentially of, in admixture:a) a compound which forms anacid on irradiation, in an amount sufficient to cleave compound b), b) acompound having at least one C--O--C or C--O--Si bond which can becleaved by the acid formed by compound a), said mixture comprising anamount of compound b) sufficient to render the mixture soluble or atleast swellable in aqueous-alkaline solution when the acid formed fromcompound a) upon irradiation cleaves compound b), and c) awater-insoluble binder which is soluble of at least swellable in aqueousalkaline solutions, said binder being present in an amount sufficient toform a uniform film when a layer of the positive-workingradiation-sensitive mixture is coated on a substrate, wherein compound(a) is an α- carbonyl-α-sulfonyldiazomethane derivative of the formula I##STR4## in which R¹ and R², independently of one another, denote analkyl-, cycloalkyl-, aryl- or heteroaryl radical any of which may beoptionally-substituted.
 2. A positive-working radiation-sensitivemixture as claimed in claim 1, wherein the radicals R¹ and R² in formulaI denote a substituted alkyl or substituted cycloalkyl radical, asubstituted aryl radical or a substituted heteroaryl radical. 37
 3. Apositive-working radiation-sensitive mixture as claimed in claim 1,wherein at least one of the radicals R¹ and R² in formula I is anoptionally-substituted alkyl radical containing 1 to 6 carbon atoms oran optionally-substituted aryl radical.
 4. A positive-workingradiation-sensitive mixture as claimed in claim 1, wherein at least oneof the radicals R¹ and R² in formula I is an optionally-substituted arylradical.
 5. A positive-working radiation-sensitive mixture as claimed inclaim 2, wherein the aryl radicals R¹ and R² are substituted by asubstituent selected from the group consisting of alkyl, alkoxy,alkoxyalkyl, cyano, and halogen.
 6. A positive-workingradiation-sensitive mixture as claimed in claim 1, wherein the mixtureis sensitive to UV light having a wavelength of 190 to 450 nm.
 7. Apositive-working radiation-sensitive mixture as claimed in claim 1,wherein the mixture is sensitive to UV light having a wavelength of 200to 400 nm.
 8. A positive-working radiation-sensitive mixture as claimedin claim 1, wherein the concentration of the acid-forming compound ofthe formula I is about 0.5 to 25% by weight, based on the total weightof solids.
 9. A positive-working radiation-sensitive mixture as claimedin claim 1, wherein the binder has an absorbance of less than about 0.5μm⁻¹ in the wavelength range to which the mixture is sensitive.
 10. Apositive-working radiation-sensitive mixture as claimed in claim 1,wherein up to about 30% by weight of said binder is a novolakcondensation resin.
 11. A positive-working radiation-sensitive mixtureas claimed in claim 9, wherein the binder contains phenolic hydroxylgroups.
 12. A positive-working radiation-sensitive mixture as claimed inclaim 9, comprising a binder concentration of about 60 to 96% by weightin the radiation-sensitive mixture, based on the total weight of theradiation-sensitive mixture.
 13. A positive-working radiation-sensitivemixture as claimed in claim 9, wherein the binder has an absorbance ofless than about 0.3 μm⁻¹ above 240 nm.
 14. A positive-workingradiation-sensitive mixture as claimed in claim 1, wherein the compoundof the formula I has the highest molar absorption of all the resistconstituents at 248 nm.
 15. A positive-working radiation-sensitivecopying material consisting essentially of:a support, and aradiation-sensitive layer of a radiation-hardenable mixture as claimedin claim 1 coated on the support.
 16. A positive-workingradiation-sensitive mixture as claimed in claim 1, wherein up to about20% by weight of said binder is a novolak condensation resin.
 17. Apositive-working radiation-sensitive mixture as claimed in claim 9,comprising a binder concentration of about 70 to 94% by weight in theradiation-sensitive mixture, based on the total weight of theradiation-sensitive mixture.
 18. A positive-working radiation-sensitivemixture as recited in claim 1, wherein compound b) is a compound havingat least one C--O--C bond.
 19. A positive-working radiation-sensitivemixture as recited in claim 1, wherein compound b) is a compound havingat least one C--O--Si bond.
 20. A positive-working radiation-sensitivemixture as recited in claim 1, wherein the binder is a mixture of (1) upto about 30% by weight of a novolak condensation resin and (2) a resinhaving an absorbance of less than about 0.5 μm⁻¹ in the wavelength rangeto which the mixture is sensitive.
 21. A positive-workingradiation-sensitive mixture as recited in claim 1, wherein the binder isa mixture of (1) up to about 20% by weight of a novalak condensationresin and (2) a resin having an absorbance of less than about 0.3 μm⁻¹in the wavelength range above 240 nm.